Emulsion polymerization of vinylidene compounds in the presence of hydroperoxides of alkyltetrahydronaphthalenes



Patented Feb. 5, 1952 EMULSION POLYMERIZATION OF VINYL- IDENE COMPOUNDS IN THE PRESENCE F HYDROPEROXIDES OF ALKYLTET- RAHYDRONAPHTHALENES William 18. Reynolds, John E. Wicklatz, and Thomas J. Kennedy, Bartlesville, 0kla., assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application December 12, 1949,

V Serial No. 132,626

7 Claims. (Cl. 26084.1)

This invention relates to an improved process for polymerizing unsaturated organic compounds while dispersed in an aqueous emulsion. In one important aspect this invention relates to the use of faster recipes at low polymerization temperatures for effecting production of synthetic rubber by emulsion polymerization of conjugated diolefins.

With the increasing interest in low temperature emulsion polymerization, many variations in recipes and procedure have been developed in the interest of economy and efiiciency in addition to the attention given to producing polymeric materials having the desired characteristics. Recipes of the redox type, that is, formulations wherein both oxidizing and reducing components are present, have been widely used. Oxidi-zing components frequently employed include materials of a peroxidic nature, and particularly compounds such as benzoyl peroxide and cumene hydroperoxide. Even though any peroxidic material might be expected to function in the capacity of the oxidant in a redox emulsion polymerization system, this is not necessarily the case since in some instances little, if any, polymerization occurs while in other cases with different peroxides the reaction takes place at a satisfactory rate. Some peroxides may function fairly satisfactorily at higher temperatures but are of little value when it is desired to carry out polymerizations at low temperatures, say below the freezing point of water.

We have now discovered that rapid conversion rates are obtained when carrying out emulsion polymerization reactions at low temperatures using recipes in which the polymerization catalyst composition comprises an oxidant and a reductant and in which the oxidizing component employed is an alkyltetrahydronaphthalene hydroperoxide, such as is formed upon reaction of free oxygen with an alkyltetrahydronaphthalene in which at least one alkyl group is attached to a completely saturated carbon atom, as discussed hereinafte'r. We have also discovered that these alkyltetrahydronaphthalene hydroperoxides are far superior to a hydroperoxide prepared from tetrahydronaphthalene itself as oxidants in catalyst compositions for emulsion polymerization reactions, and with some recipes 2 it is possible to effect satisfactory polymerization without having present in the polymerization system any salt of a heavy metal, such as iron.

The hydroperoxides which are applicable in this invention can be represented by the formula R x R wherein one X is an -0OH group and each other X is hydrogen, each R is of the group consisting of hydrogen and an alkyl group with at least one R being an alkyl group and with the sum of the carbon atoms in the R groups not greater than ten, and each R is of the group consisting 5,8-dichloro1,2,3,4-tetrahydronaphthalene hy--' droperoxide, 5 phenyl-1,2,3,4-tetrahydronaphthalenehydroperoxide, 5-benzyl-1,2,3,4 tetrahydronaphthalene hydroperoxide, 5-phenoxy-L2 3,4-tetrahydronaphthalene hydroperoxide, 5, 7,8-tetrafluoro-1-methyl-l,2,3,4-tetrahydr-onaphthalene hydroperoxide and l-methyl-4-ethyl-L- 51 2,3,4-tetrahydronaphthalene hydroperoxide. An object of this invention is to polymerizeunsaturated organic compounds. Another object of this invention is to produce synthetic rubber. A further object of this invention is to polymerize a monomeric material comprising a conjugated diene while dispersed in an aqueous medium. Still another object of this invention is to effect rapid polymerization at low polymerization temperatures of monomeric materials dispersed in an aqueous media. Further objects and advantages of this invention will become apparent, to one skilled in the art, from the accompanying disclosure and discussion.

The hydroperoxides used in the practice of this invention can easily be prepared by simple oxidation, with free oxygen, of the corresponding alkyltetrahydronaphthalene compound. The alkyltetrahydronaphthalene compound to be oxidized is placed in a reactor, together with an inert diluent if such is desired, heated to the desired temperature, and oxygen introduced at a controlled rate throughout the reaction period. The mixture is agitated during the reaction which is generally allowed to continue for about one to ten hours. The temperature employed is preferably maintained between 50 and 160 0., although in some instances it might be desirable to operate outside this range, that is, at either higher or lower temperatures. At the conclusion of the reaction the oxidized mixture may be employed as such, that is, as a solution of the hydroperoxide in the reaction mixture, or unreacted material may be removed and residualhydroperoxide material employed.

When oxidizing an alkyltetrahydronaphtalene compound in the manner described, the resulting product is frequently referred to as a hydroperoxide composition rather than a single hydroperoxide. The major active ingredient in such a composition is a monohydroperoxide, or mixture of monohydroperoxides. The hydroperoxide group appears to result from introduction of two oxygen atoms between one of the carbon atoms of the saturated, or hydrogenated, ring which is directly attached to the aromatic ring and the single hydrogen atom attached thereto. In a hydrocarbon such as 1, 2, 3, 4-tetrahydronaphthalene, there are two alpha positions, each of which is susceptible to oxidation. When an alkyl group is present in one of these'positions, thereby resulting in a tertiary carbon atom, oxidation appears to occur preferably at this point. In the These compounds have the general formula nnmcnxcnxnm 1n (cnxcrno nNHR where each R contains not more than eight carbon atoms and is of the group consisting of hydrogen, aliphatic, cycloaliphatic, aromatic, oleflnic, and cyclooleflnic radicals, and each X contains not more than three carbon atoms and 'is of the group consisting of hydrogen and allphatic radicals, m is an integer between 0 and 8, inclusive, and n is an integer of the group consisting of 0 and 1 and is 1 when m is greater than 0. Each of the foregoing radicals (other than hydrogen) can be completely hydrocarbon in character, and can be of mixed character when containing six or more carbon atoms, such as alkylcycloalkyl, aralkyl, alkaryl groups, and the like, and can also have non-hydrocarbon substituents, some of which will have the effect of making them more water-soluble and less oil- (hydrocarbom-soluble; particularly useful nonhydrocarbon substituents include oxygen in the form of hydroxy and ether compounds, sulfur in similar compounds (1. e. mercapto compounds and thioethers) and halogen compounds. In

' such recipes, such a polyamino compound apmethod for the production of hydroperoxides just outlined, even though the structure of the hydrocarbon is such that oxidation may occur at more than one of the carbon atoms of the saturated ring, the resulting product appears to be only the monohydroperoxide or mixture of monohydroperoxides. Other methods of producing such hydroperoxides, known to the art, can be used to produce the hydroperoxides which are used in the process forming the present invention. These hydroperoxide compositions not only give faster polymerization rates when used to effect emulsion polymerizations, but their use also frequently results in a more uniform reaction rate over a given reaction period than do hydroperoxides heretofore used. These advantages are particularly pronounced at polymerization temperatures below 10 C., and down to polymerization temperatures as low as or C., or.lower.

We use the hydroperoxides discuossed herein as oxidants in polymerization recipes at low polymerization temperatures, 1. e. from about 10 C., or just above the freezing point of water, to well below the freezing point of water, such as 40 C. or lower. The recipe will also include a compound or composition which will act as a repears to act as a reductant, and no other activating ingredients, such as compounds of polyvalent-multivalent metals, or reducing ingredients, such as a reducing sugar, need be present in order to obtain satisfactory and rapid polymerization of the monomeric material, even at subfreezing temperatures. The amount of polyamino compound used to obtain optimum results also is dependent upon other ingredients in the recipe. Preferred results are usually obtained with between 0.02 to 5 parts by weight, per 100 parts of monomeric material, of the polyamino compound. In other recipes a composition is used which comprises one compound which is an oxidation catalyst, or activator, and another different compound which is a reductant. The oxidation catalyst is generally selected from a group of materials consisting of compounds of metals such as iron, manganese, copper, vanadiui'n, cobalt, etc. In general it is assumed that the metal must be a multivalent metal and in 'such a condition that it can change its valence state reversibly. The other ingredient ordinarily present is a reductant, and is usually an organic material such as a reducing sugar or other easily oxidizable organic compound having a hydroxy group on a carbon atom directly attached to an aldehyde or ketone group. Compounds frequently employed in this capacity are onds.

in the dual role of reductant and oxidation cata: lyst. One commonly used oxidation catalyst is an iron pyrophosphate, and is separately made up in aqueous solution from a ferrous salt, such as ferrous sulfate, and a pyrophosphate of an alkali metal, such as sodium or potassium.

When a ferrous pyrophosphate activator is used, it is preferably prepared by admixing a ferrous salt, such as ferrous sulfate, with a pyrophosphate of an alkali metal, such as sodium or potassium, and water and heating this mixture, preferably for the length of time required for maximum activity. A reaction occurs between the salts, as evidenced by the formation of a grayish-green precipitate. When preparing the activator the mixture is generally heated above 50 C., for variable periods depending upon the temperature. For example, if the mixture is boiled, a period of twenty minutes or less is willcient to produce the desired activity, and the time of boiling may even be as low as 30 sec- One convenient method of operationinvolves maintaining the temperature of the acti-'- vator solution at about 60 C. for a. period of heating ranging from to 30 minutes. Prior to heating the activator mixture the vessel is usually flushed with an inert gas such as nitrogen. In general it is preferred to heat the mixture below the boiling point, say at a temperature around 55 to 75 C.

In cases where the activator is prepared just prior to use, it is generally employed in the form of an aqueous dispersion as described above. However, the solid activator may be isolated and the crystalline product used, and in this form it is preferred in some instances. Subsequent to heating the activator mixture, it is cooled to around room temperature and the solid material separated by centrifugation, filtration, or other suitable means, after which it is dried. Drying may be accomplished in vacuo in the presence of a suitable drying agent, such as calcium chloride, and in an inert atmosphere such as nitro gen. When using this crystalline product in emulsion polymerization reactions, it is generally charged to the reactor just prior to introduction of the butadiene. This crystalline material is believed to be a sodium ferrous pyrophosphate complex, such as might be exemplified by the formula 2NazFeP2O7.Na4P2O7, or perhaps In any event the complex whatever its composition, is only slightly soluble in water and is one active form of ferrous ion and pyrophosphate which can be successfully used in our invention. It may be incorporated in the polymerization mixture as such, or dissolved in sufiicient water to produce solution. Other forms of multivalent metal and pyrophosphate may also be used, so long as there is present in the reacting mixture a soluble form of a multivalent metal, capable of existing in two valence states and present primarily in the lower of two valence states, and a pyrophosphate.

The amounts of activator ingredients are usually expressed i terms of the monomers charged. The mu'tivalent metal should be within the range of 0.10 to 3 millimols per 100 parts by weight of monomers, with 0.2 to 2.5 millimols being generally preferred. The amount of pyrophosphate should be within the range of 0.10 to 5.6 millimols based on 100 parts by weight of monomers; however, the narrower range of 0.2 to

- om'eric material, particularly when a batch-type or semi-batch-type operation is carried out, the reactor is usually first charged with the aqueous medium, which contains the desired emulsifying agent, and the monomeric material is then admixed with agitation of the contents. At the same time a reaction modifier, such as a mercaptan, is also included, usually in solution in at least a part of the monomeric material. An activator solution and an oxidant are separately added to the reaction mixture, and reaction then proceeds. A preferred manner of adding these two constituents is usually to have the activator solution incorporated in the aqueous medium prior to addition of the monomeric material, and to add the oxidant as the last ingredient. Sometimes, however, satisfactory polymerization results can be obtained when this procedure is reversed. It is also sometimes the practice to add portions of one or the other of the activator solutions and oxidant intermittently, or continuously, during the course of the'reaction. If the operation is carried out continuously, streams of the various ingredients are admixed in somewhat the same order prior to their final introduction into the polymerization reaction zone.

As previously stated, it is usually desirable that the multivalent metal be present in its lower valence state. With some recipes, it is unnecessary to include an organic reducing agent either in the activator solution or in the polymerization mixture. However, particularly at temperatures above 0 C., a faster reaction is sometimes obtained with some recipes when a small amount of an organic reducing agent, such as a reducing sugar, is included in the polymerization recipe, and it is frequently more desirable to incorporate this in the reaction system by first including it in the activator solution along with the other ingredients. When the multivalent ion is present in its higher valence state, it is usually necessary to include in the activator solution an organic reducing agent. As a result the multivalent ion will be partially reduced and a substantial amount of the multivalent ion will be present in its lower valence state when the activator solution is ready for addition to the polymerization mixture.

The monomeric material polymerized to produce polymers by the process of this invention comprises unsaturated organic compounds which generally contain the characteristic structure CHz:C and, in most cases, have at least one of the disconnected valences attached to an electronegative group, that is, a group which increases the polar character of the molecule such as a. chlorine group or an organic group containing a double or triple bond such as vinyl, phenyl, cyano, carboxy or the like. Included in this class of monomers are the conjugated butadienes or 1,3-butadienes such as butadiene (1,3-butadiene), 2,3-dimethyl-l,3-' butadiene, isoprene, piperylene, 3-furyl-1,3-butadiene, 3-methoxy-1,3-butadiene and the like; haloprenes, such as chloroprene (2-ch1oro-1,3 butadiene), bromoprene, methyl chloroprene (2-ohloro-3-methyll,3-butadiene), and the like; aryl olefins such asstyrene, various alkyl styrenes, p-chlorostyrene, p-methoxy-styrene,,

alpha methylstyrene, vinylnaphthalene and similar derivaties thereof. and the like; acrylic and substituted acrylic acids .and their esters,

nitriles and amides such as acrylic acid, meth-" acrylonitrile, methacrylamide and the like,

methyl isopropenyl ketone, methyl vinyl, ketone, methyl vinyl ether, vinylethinyl alkyl carbinols, vinyl acetate, vinyl chloride, vinylidene chloride, vinylfurane,"vinylcarbazole, vinylacetylene and other unsaturated hydrocarbons, esters, alcohols, acids, ethers, etc., of the types described. Such unsaturated compounds may be polymerized alone. in which case simple linear polymers are formed, or mixtures of two or more of such compounds which are copolymerizable with each other in aqueous emulsion may be polymerized to form linear copolymers.

The process of this invention is particularly effective when the monomeric material polymerized is a polymerizable aliphatic conjugated diolefln or a mixture of such a conjugated dioleiln with lesser amounts of one or more other compounds containing an active CH2=C group which are copolymerizable therewith such as aryi oleflns, acrylic and substituted acrylic acids, esters, nitriles and amides. methyl isopropenyl ketone, vinyle chloride, and similar compounds mentioned hereinabove. In this case the products of the polymerization are high molecular weight linear polymers and copolymers which are rubbery in character and may be called synthetic rubber. Although. as can be readily deduced from the foregoing, there is a host of possible reactants, the most readily and commercially available monomers at present are butadiene it self (1,3-butadiene) and styrene. The invention will, therefore, be more particularly discussed and exemplified with reference to these typical reactants. With these specific monomers, it is usually preferred to use them together, in relative-ratios of butadiene to styrene be tween 65:35 and 90:10 by weight.

It is generally preferred that the emulsion be of an oil in water type, with the ratio of aqueous medium to monomeric material between about 05:1 and about 2.75:1, in parts by weight. It is frequently desirable to include water-soluble components in the aqueous phase, particularly when the polymerization temperatures are below freezing. Inorganic salts and alcohols can be so used. Alcohols which are applicable, when operating at low temperatures, comprise watersoluble compounds of both the monohydric and polyhydric types, and include methyl alcohol, ethylene glycol, glycerine, erythritol, and the like. The amount of alcoholic ingredient used in a polymerization recipe must be sufllcient to prevent freezing of the aqueous phase and generally ranges from 20 to 80 parts per 100 parts of monomers charged. In most cases the amount of water employed is sufficient to make the total quantity of the alcohol-water mixture equal 150 to 200 parts. In cases ,where it is desired to use a larger quantity of the alcohol-water mixture, say around 250 parts, the amount of alcohol may be increased to as much as 120 parts. It is preferred that the alcohol be such that it is substantially insoluble in the non-aqueous phase, and that 90 per cent, or more, of the alcohol present he in the aqueous phase. A high-boiling alcohol such as glycerine is diflicult to recover continuously. tants is preferably at least as great as the total from the resulting serum; a low-boiling alcohol such as methanol is easily removed and frequently preferred. Other aliphatic alcohols which are higher-boiling than methanol, such as a propanol, are frequently less satisfactory. If the resulting latex tends to gel at low reaction temperatures, a larger proportion of aqueous phase should be used. In the practice of the invention suitable means will be necessary to establish and maintain an emulsion and to remove reaction heat to maintain a desired reaction temperature. The polymerization may be conducted in batches, semicontinuously, or

The total pressure on the reacvapor pressure of the mixture, so that the initial reactants will be present in liquid phase. Usually 50 to 98 per cent of the monomeric material 1 p ymerized.

It is one of the outstanding advantages of the use of the hydroperoxides, as disclosed herein, that it is feasible to produce high solids" latices, i. e. latices resulting from the use of an amount of aqueous medium in the lower part of the range disclosed, i. e. a ratio of aqueous phase to monomeric material between 0.5:1 to 1:1 and an extent of conversion in the higher part of the range disclosed, i. e. from 70 per cent conversion to complete conversion.

Emulsifying agents which are applicable in these low temperature polymerizations are materials such as potassium laurate, potassium oleate, and the like, and salts of rosin acids. However, other emulsifying agents, such as nonionic emulsifying agents, salts of alkyl aromatic sulfonic acids, salts of alkyl sulfates, and the like which will produce favorable results under the conditions of the reaction, can also be used in practicing the invention, either alone or in admixture with soaps. The amount and kind of emulsifier used to obtain optimum results is somewhat dependent upon the relative amounts of monomeric material and aqueous phase, the

reaction temperature, and the other ingredients of the polymerization mixture. Usually an amount between about 0.3 and 5 parts per 100 parts of monomeric material will be found to be suilicient.

The pH of the aqueous phase may be varied over a rather wide range without producing deleterious effects on the conversion rate or the properties of the polymer. In general the pH can be within the range of 9 to 12, with the nar-' rower range of 9.5 to 10.5 being most generally preferred, except when a polyamino compound is used as a reductant, in which case a somewhat higher pH should usually be used.

In preparing synthetic rubber by polymerizing conjugated dienes by the process of the in-'" vention, it is usually desirable to use a polymerization modifying agent, as is usually true in other polymerizations to produce synthetic rubber. Preferred polymerization modifiers for use in the process of the present invention are alkyl mercaptans. and these may be of primary, secondary, or tertiary configurations, and generally range from Cs to C10 compounds, but may have more or fewer carbon atoms per molecule. Mixtures or blends of mercaptans are also frequently considered desirable and in many cases are preferred to the pure compounds. The amount of mercaptan employed will vary, depending upon the particular compound or blend chosen, the operating temperature, the freezing point depressant employed, and the results desired. In

general, the greater modification is obtained when operating at low temperatures and therefore a smaller amount of mercaptan is added to yield a product of a given Mooney value, than is used athigher temperatures. In the case of tertiary mercaptanafsuch as tertiary C1: mercaptans, blends of tertiary C12, C14, and C16 mercaptans, and thelike, satisfactory modification is obtained with 0.05 to 0.3 part mercaptan per 100 parts monomers, but smaller or larger amounts may be employed in some instances. .In fact, amounts as large as 2.0 parts per 100 parts of monomers may be used. Thus the amount of mercaptan is adjusted to suit the case at hand.

The amount of hydroperoxide used to obtain an optimum reaction rate will depend upon the other reaction conditions, and particularly upon the type of polymerization recipe used. The amount is generally expressed in millimols per 100 parts of monomeric material, using in each instance the same units of weight throughout, 1. e. when the monomeric material is measured in pounds the hydroperoxide is measured in millipound mols. The same is true for other ingredients of the polymerization recipe. An optimum rate of polymerization is usually obtained with the amount of hydroperoxide between 0.1 and millimols per 100 parts by weight of monomeric material. The hydroperoxide can frequently be easily separated from accompanying materials by converting it to a corresponding salt of an alkali metal, which is usually a crystalline material in a pure or concentrated state at centration of hydroperoxide at this point was 21.7 per cent by weight. Portions of this material were used to supply the resulting i-methyl- 1,2,3,4 tetrahydronaphthalene 1 hydroperoxide, in the amounts indicated, as the oxidant in the following polymerization recipe:

1 Dresinate 214'; solution ph 10. A blend of tertiary C", C, and O1; aliphatic mercaptans in a ratio of 3:111 parts by weight.

The activator composition was prepared by heating a mixture of the ferrous sulfate, potassium pyrophosphate, and water at C. for 20 minutes.

The dextrose, potassium hydroxide, and 25 parts water were heated at C. for 25 minutes and added to the soap solution. The mercaptan dissolved in the styrene was then added, the temperature adjusted to the desired level, the butadiene introduced followed by the hydroperoxide, and finally the activator composition. Polymerization was effected at 5 C. The time-conversion data'are recorded below together with the amounts of hydroperoxide employed.

Hydroperoxide Conversion, Per Cent resomulo, 5

Type Parts Millimols 2 hrs. 5 hrs. 7 DIS.

l-Methyl-l,2,3,4-tetrahydronaphalone. 0. oer-7 o. 375 0. 14 o. 13. 1 41. 0 5a. 4 2:2 as it a; iii 11 0 0114 210 81 6 26: 2 3s: a

atmospheric temperatures, and separating the salt This salt can be used as an active form of the hydroperoxide, since it is promptly converted to the hydroperoxide by hydrolysis when the salt is admixed with the aqueous medium of the polymerization reaction mixture.

Advantages of this invention are illustrated by the following examples. The reactants, and their proportions, and the other specific ingredients of the recipes are presented as being typical and should not be construed to limit the inven- 1,2,3,4 tetrahydronaphthalene-i-hydroperoxide was prepared in a manner similar to that described for the preparation of the alkyl com-' above. The data obtained from four runs are tion unduly. herewith presented.

Hydroperoxide M015 H Conversion, Per Cent ydrogg peroxide per Type Parts Miilimols M01 Fe++ 2 hrs. 5 hrs. 7 hrs.

l,2,3,4-Tetrahydronaphthalene 0. 0615 0. 375 0. 14 O. 75 6. 7 9. 1 10. 0 D 0.082 0. 50 U. 14 1.0 2.9 5.4 8.6 0. 75 0. 14 1. 5 4. 2 14. 3 23. 6 1. 0 0. 14 2. 0 4. 0 12. 7 18. 0

Example I l-methyl-1,2,3,4-tetrahydronaphthalene (100 parts) was oxidized by charging it to a reactor together with 0.75 part of the potassium salt of diisopropylbenzene hydroperoxide, this latter compound being employed as an initiator for the reaction. The temperature was adjusted to 85 C. and dry oxygen introduced over a 4.5 hour In 700 parts by weight of n-decane there is dissolved 200 parts of 2-ethyl-5-methoxy-l,2,3,4-

perjod while the mixture was stirred. The con- 7 tetrahydronaphthalene, together with 2 parts of .11 the potassium salt of diisopropylbenzene hydroperoxide. This solution is then treated with -"gaseous oxygen at 100 C., with vaporized decane being returned from eilluent vapors by a reflux condenser. A resulting solution of hydroperoxide, primarily 2-ethyl-5-methoxy-l,2,3,4-tetrahydronaphthalene-2-hydroperoxide, is used in the following recipe. I

Partsqby weight Same as in Example I.

To the aqueous phase containing methanol, emulsifier, and potassium phosphate is added the butadiene, mercaptan, and hydroperoxide. The

temperature is then adjusted to l0 C., and anaqueous .added. A conversion of about 48 per cent is obtained in hours, and resulting polymeric synthetic rubber is recovered.

solution of tetraethylenepentamine Using the same recipe, but with a hydroperoxide prepared by oxidizing tetralin (1,2,31,4- tetrahydronaphthalene) as the hydroperoxide, in the same molecular amount, only 8 per cent conversion is obtained in 24 hours.

As will be evident to those skilled in the art, various modifications of this invention can be made, or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

We claim:

1. An improved process for the production of synthetic rubber, which comprises establishing and maintaining at a polymerization temperature between 10 and 40 C. an emulsion of an aqueous phase having a pH between 9 and 12, a liquid monomeric material comprising a major amount oi? 1,3-butadiene and a minor amount of styrene,

an alkali metal soap emulsifying agent, an alkyl mercaptan having between eight and sixteen carbon atoms per molecule, and a polymerization catalyst composition comprising 0.1 to 10 millimols of 1-methyl-1,2,13,4-tetrahydronaphthalenel-hydroperoxide together with 0.1 to 3 millimols of an alkali metal ferrous pyrophosphate complex and a reducing sugar, said parts being parts by weight per 100 parts of said monomeric material.

2. An improved process for the production of synthetic rubber, ,which comprises establishin and maintaining at a polymerization temperature between 10 and 40 C. an emulsion of an aqueous phase having a pH between 9 and 12, a liquid monomeric material comprising a major amount of 1,3-butadiene and a minor amount of styrene, an alkali metal soap emulsifying agent, an alkyl mercaptan having between eight and sixteen carbon atoms per molecule, and a polymerization catalyst composition comprising 0.1 to 10 millimols of a l-alkyl-1,2,3,4-tetrahydronapthalenel-hydroperoxide having not more than thirty carbon atoms per molecule and not more than ten carbon atoms in said alkyl group together with 0.1 to 3 millimols of an alkali metal ferrous pyrophosphate complex and a reducing sugar,

-'synt hetic rubber, which comprises establishing and maintaining at a polymerization temperature between 10 and 40 C. an emulsion of an aqueous phase having a pH between 9 and 12, a liquid monomeric material comprising a major amount ,of 1,3-butadiene and a minor amount of styrene, an alkali metal soap emulsifying agent, an alkyl mercaptan having between eight and sixteen carbon atoms per molecule, and a polymerization catalyst composition comprising 0.1 to 10 millimols of an alkyl tetrahydronaphthalene hydroperoxide having not more than thirty carbon atoms per molecule and not more than ten carbon atoms in said alkyl group and having said alkyl group and the hydroperoxide roup attached to a carbon atom of said tetrahydronaphthalene nucleus which in 'turn is attached to two additional carbon atoms in said nucleus together with 0.1 to 3 millimols of an alkali metal ferrous pyrophosphate complex and a reducing sugar, said parts being Parts by weight per 100 parts of said monomeric material.

4. In the production of synthetic rubber by polymerization of. a monomeric material comprising a conjugated diene having not more than six carbon atoms per-molecule while dispersed in an aqueous medium in the presence of a polymerization catalyst composition comprising an oxidant and a reductant, the improvement which comprises polymerizing said monomeric material in the presence of 0.1 to 10 millimols of 1 methyl 1,2,3,4 tetrahydronaphthalene 1 hydroperoxide per 100 parts by weight of said monomeric material as said oxidant.

5. In the polymerization of a monomeric material comprising a conjugated diene having not more than six carbon atoms per molecule while dispersed in an aqueous medium in the presence of a polymerization catalyst composition comprising an oxidant and a reductant, the improvement which comprises polymerizing said monomeric material in the presence of an alkyltetrahydronaphthalene hydroperoxide having not more than thirty carbon atoms per molecule and not more than ten carbon atoms in said alkyl group and having said alkyl group and the hydroperoxide group attached to a carbon atom of said tetrahydronaphthalene nucleus which in turn is attached to two additional carbon atoms in said nucleus as said oxidant.

6. In the production of a polymeric material of high molecular weight by polymerization of a monomeric material comprising a conjugated diene having not more than six carbon atoms Y per molecule while dispersed in an aqueous medium in the presence of a polymerization catalyst comprising an oxidant and a reductant,

the improvement which comprises polymerizing said monomeric material at a polymerization temperature between 10 and --40 C. in the pres- 13 merizable when dispersed in an aqueous medium in the presence of a polymerization catalyst composition comprising an oxidant and a reductant, the improvement which comprises polymerizing such a monomeric material while dispersed in an 5 aqueous medium in the presence of an alkyltetrahydronaphthalene hydroperoxide having not more than thirty carbon atoms per molecule and not more than ten carbon atoms in said alkyl group and having said alkyl group and the hydroperoxide group attached to a carbon atom of said tetrahydronaphthalene nucleus which in turn is 14 attached to two additional carbon atoms in said nucleus as said oxidant.

WILLIAM B. REYNOLDS. JOHN E. WICKLATZ. THOMAS J. KENNEDY.

REFERENCES CITED The following references are or record in the file of this patent:

UNITED STATES PATENTS Name Date 

1. AN IMPROVED PROCESS FOR THE PRODUCTION OF SYNTHETIC RUBBER, WHICH COMPRISES ESTABLISHING AND MAINTAINING AT A POLYMERIZATION TEMPERATURE BETWEEN 10 AND-40* C. AN EMULSION OF AN AQUEOUS PHASE HAVING A PH BETWEEN 9 AND 12, A LIQUID MONOMERIC MATERIAL COMPRISING A MAJOR AMOUNT OF 1,3-BUTADINE AND A MINOR AMOUNT OF STYRENE AN ALKALI METAL SOAP EMULSIFYING AGENT, AN ALKYL MERCAPTAN HAVING BETWEEN EIGHT AND SIXTEEN CARBON ATOMS PER MOLECULE, AND A POLYMERIZATION CATALYST COMPOSITION COMPRISING 0.1 TO 10 MILLIMOLS OF 1-METHYL-1,2,3,4-TETRAHYDRONAPHTHALENE1-HYDROPEROXIDE TOGETHER WITH 0.1 TO 3 MILLIMOLS OF AN ALKALI METAL FERROUS PYROPHOSPHATE COMPLEX AND A REDUCING SUGAR, SAID PARTS BEING PARTS BY WEIGHT PER 100 PARTS OF SAID MONOMERIC MATERIAL. 